1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus.
2. Description of Related Art
In general, an electrophotographic image forming apparatus (such as a printer, a copy machine, and a fax machine) is configured to irradiate (expose) a charged photoconductor with (to) laser light based on image data to form an electrostatic latent image on the surface of the photoconductor. The electrostatic latent image is then visualized by supplying toner from a developing device to the photoconductor (image carrier) on which the electrostatic latent image is formed, whereby a toner image is formed. Further, the toner image is directly or indirectly transferred to a sheet, followed by heating and pressurization, whereby an image is formed on the sheet.
For example, in an image forming apparatus of an intermediate transfer belt type, a toner image formed on a photoconductor is transferred to an intermediate transfer belt, and the toner image transferred to the intermediate transfer belt is transferred to a sheet.
In this process, the toner is not completely transferred to the sheet and remains on the surface of the intermediate transfer belt. The remaining toner hinders subsequent image forming, and causes a problem that a favorable transfer image cannot be obtained.
In the above-mentioned cleaning apparatus, a cleaning blade is brought into pressure contact with the surface of the intermediate transfer belt to remove the toner remaining on the intermediate transfer belt. As the image formation process is continuously performed, foreign matter 230 (mainly, aggregates of paper dust and the like) is gathered and gradually accumulated at a part (hereinafter referred to as “blade edge 212”) where cleaning blade 210 makes pressure contact with intermediate transfer belt 220, as illustrated in FIG. 1. This leads to a state where foreign matter 230 is sandwiched between cleaning blade 210 and intermediate transfer belt 220, or in other words, a state where blade edge 212 of cleaning blade 210 is separated from the surface of intermediate transfer belt 220. When the state where blade edge 212 is separated from the surface of intermediate transfer belt 220 is continued, part 250 (hereinafter referred to as “toner 250”) of toner 240 remaining on intermediate transfer belt 220 may pass through a space between cleaning blade 210 and intermediate transfer belt 220 where foreign matter 230 does not exist, in the rotational axis direction of intermediate transfer belt 220.
When toner 250 passes through the space between cleaning blade 210 and intermediate transfer belt 220, that is, when a cleaning defect is caused in the above-mentioned manner, remaining toner 250 is transferred onto the image formed by the next image formation process and becomes image noise in a black streak form. Thus, image noise is caused.
In order to prevent such a cleaning defect, conventionally, there has been proposed a technique in which an intermediate transfer belt is reversed to remove the foreign matter sandwiched between a cleaning blade and an intermediate transfer belt (see, for example, Japanese Patent Application Laid-Open No. 2007-171395).
However, with the conventional technique in which the intermediate transfer belt is reversed, when the foreign matter once removed from the space between the cleaning blade and the intermediate transfer belt again enters the blade edge, the foreign matter is sometimes gathered at the blade edge and sandwiched between the cleaning blade and the intermediate transfer belt. As such, the conventional techniques could not have completely eliminated the risk that toner pass through the space between the cleaning blade and the intermediate transfer belt, that is, the risk that cleaning defect is caused.